UPDATE: I talked with Meridian America this morning and they suspect the problem is with the USB to serial adapter. Meridian suggested I get a Keyspan adapter and try again. So I will do that.

Continued thanks for the suggestions.

2-Channel: Mer 800, Wadia 170i, Ipod, Berkeley DAC, Clayton M300 Amps, Martin Logan Spires
Multi-channel: Oppo BDP-83, Mer 800, HD621, Mer 861, Clayton/Rowland/Classe amps, Martin Logan Spires & Stage, Revel Embrace, REL Stentor